osmoregulation and negative feedback Flashcards
define homeostasis
the maintenance of internal environment
what is the importance of homeostasis
- enzymes that are sensitive to change in temperature and pH - this therefore avoids denaturing
- changes to water potential of blood and tissue and tissue fluid may cause cells to shrink or expand
what is positive feedback
when a deviation from an optimum causes changes that result in an even greater deviation from the optimum
what is negative feedback
changes that return systems back to optimum
what is an ectotherm
organisms that gain heat from the environment
what is an endotherm
organisms that generate their own heat
what is piloerection
where hairs stand on end
what will happen when your body is cold
shivering
- piloerection
- increased metabolic rate
- vasoconstriction
- behavioural changes
what happens when you are too hot
- vasodilation
-sweat - pilorelaxation
- behavioural chnages
what is the function of glucagon
glucagon causes liver cells to convert glycogen to glucose which is released into the blood - therefore raising blood glucose levels `
what is the function insulin
it will increase the uptake of glucose by cells and its conversion to glycogen and fat
which system do insulin and glucagon work on
negative feedback
what happens if temp of the blood is too high
thermoreceptors in the hypothalamus send more impulses to cool down
define gluconeogenesis
conversion of non-carbohydrates into glucose when glycogen supply is exhausted - usually amino acids or glycerol
define glycogenesis
conversion of glucose into glycogen
define glycogenolysis
breakdown of glycogen to glucose via hydrolysis
where does gluconeogenesis, glycogenesis and glycogenolysis occur
in the liver
where are the receptors that detect blood glucose levels located
islets of Langerhans
what do alpha cells secrete
glucagon
what do beta cells secrete
insulin
what do the islets of langerhan contain
alpha and beta cells
what happens when blood glucose levels are too slow
alpha and beta cells in the islets of Langerhan will detect this stimuli
the alpha cell will stop secreting insulin.
the beta cell containing glucagon will be secreted and will bind to the cell surface membrane of liver cells. this binding will stimulate enzymes associated with glycogenolysis and gluconeogenesis
glucose is released from the cells and blood glucose concentration is increased
describe the mechanism of insulin
beta cells detect the increase in blood-glucose levels
- glucose moves into beta cells via facilitated diffusion
- this will cause insulin containing vesicles to move towards the cell surface membrane where they release insulin into the capillaries.
- insulin binds to specific receptors of target cells #.
this will stimulate the cells to add more glucose transporter proteins to their cell surface membrane which increases the cells permeability to glucose
- rate of fac d into the cells increases lowering blood glucose levels
- insulin binding to receptor on liver cells causes the increase of uptake of glucose in the liver by stimulating glycogenesis which converts glucose to glycogen. this will lower blood glucose levels in the liver which will help to maintain a conc grad between capillaries and liver cells
what is type 1 diabetes
where the body does produce enough insulin
what is the result of type 2 diabetes
it is due glycoprotein receptors being unresponsive to insulin
what is the name of homeostatic control of water potential
osmoregulation
what is the function of the fibrous capsule
a protective membrane around the kidney
what is the cortex
kidney context
a lighter coloured outer made up of renal capsules, convuluted tubules and blood vessels
what is the medulla
kidney context
a darker coloured inner region made of loops of henele, collecting ducts and blood vessels
what the function of renal pelvis
a funnel shaped cavity that collects urine into the ureter
what si the function of the ureter
a tube that carries urine tot he bladder
what is the function renal artery
supplies the kidney with blood from heart via aorta
what is the function of the renal vein
returns blood to the heart via the vena cava
what is the function of the renal capsule
sometimes called bowmans capsule
- the closed end at the start of the nephron. it is cup shaped and surrounded by a mass of blood capillaries called the glomerulus - the inner layer of the renal capsule is made up of podocytes
what is the proximal convoluted tubule
a series of small loops surrounded by blood capillaries. its walls are made of epithelial cells which have microvilli for large SA
what components make up the nephron
- proximal convoluted tubules
- renal capsule
-loop of Henele - distal convoluted tubule
- collecting duct
what is the distal convoluted tubule
a series of loops surrounded by blood capilliaries. its walls are made of epithelial cells, but it is surrounded by fewer capillaries than the proximal tubule
what id the function of the collecting duct
a tube into which a number of distal convoluted tubules from a number of nephrons empty. it is lined with epithlal cells
what is the afferent arteriole
a tiny vessel that ultimately arises from the renal artery and supplies the nephron with blood
what si the glomerulus
a many branched knot of capillaries from fluid is forced out.
what is the efferent
a tiny vessel that leaves the renal capsule
what is the difference in the efferent and the affreent
the efferent has a smaller diameter - therefore has a pressure
how does the nephron carry out osmoregulation
- the formation of glomerulus by ultrafiltration
- the reabsorption of glucose and water by the PCT
maintance of a sodium ions in the medulla by the loop henle - reabsorbed of water by the distal convoluted and collecting ducts
what is a podocyte
a tiny finger like projection with gaps in between them
where does the ascending limb of the loop of henle go
drains into the Distal convoluted tubule
where does the descending limb of the loop of henle g
Medulla
what is the function of the loop of Henle
allows Na+ and Cl- to be transferred from the ascending limb to the descending limb. the overall effect is to increase the concentration of salt in filtrate therefore there will be a low water potential
which hormone is the permeability of the DCT and the collecting duct controlled by
ADH
what is good about the loop of Henle
the water potential set up by the loop of Henle allows water to be absorbed along the whole length of the collecting duct
REMEMBER
water is absorbed into the blood not just the surrounding tissue
how is the PCT adapted for max reabsorption
- folded membrane to give large surface area
- lots of membrane proteins for facilitated diffusion
-lots of ribosomes to make such proteins - lots of mitochondria to provide the ATP for protein synthesis and active transport which could be used to reabsorb the molecule
EXIT EFFERENT
leAve afferent
what is an aquaporin
channel proteins that form pores in the membrane facilitating transport of water molecules
which molecules cannot be forced out o f the capillary in ultrafiltration
blood cells and proteins - they are too large
what is ultrafiltration
due to differences in hydrostatic pressure in the efferent and afferent arteriole. water urea, mineral ions and glucose are squeezed out of the capilliary and into the renal capsule
